1. Field of the Invention
The present invention generally relates to metrology systems and methods.
2. Description of the Related Art
The following description and examples are not admitted to be prior art by virtue of their inclusion in this section.
Metrology processes are performed on wafers at various points in a semiconductor manufacturing process to determine a variety of characteristics of the wafers such as a width of a patterned structure on the wafer, a thickness of a film formed on the wafer, and overlay of patterned structures on one layer of the wafer with respect to patterned structures on another layer of the wafer. Optical critical dimension (CD) metrology is currently performed using either spectroscopic scatterometry or angle-resolved scatterometry. Optical overlay metrology is performed using either imaging methods or scatterometry-based methods (both spectroscopic and angle-resolved). Film metrology is performed using spectroscopic ellipsometry. An example of a spectroscopic ellipsometer is illustrated in U.S. Pat. No. 5,859,424 to Norton et al., which is incorporated by reference as if fully set forth herein.
However, the currently used metrology methods described above have a number of disadvantages. For example, currently optical CD metrology methods are limited to larger grating target sizes (e.g., 50 microns by 50 microns). Similarly, scatterometry-based overlay methods are limited in the minimum grating cell size to 15 microns by 15 microns. Another disadvantage of the old methods are that scatterometry-based overlay metrology and imaging-based overlay metrology are implemented on totally separate platforms.
Accordingly, it may be advantageous to develop metrology methods and systems that do not have one or more of the disadvantages described above.